I have my motor tore apart and have sanded all the blistering paint.
Much bare metal has been exposed.
Do I prime lower unit, exhaust, mid section etc or just use OEM paint?
you should use base primer paint, without any base paint its dificult to recive good sticking
i'm thinking to paint my Jo 9.9 with powder paint, hardening in temperature between 120 -200 celcius degree
Yes, Zinc Chromate, usually a nice greeny yellow colour and stinks to high heaven. Use it then regular primer, the zinc takes many coats to cover properly unless you spray with regular primer..
Good information as stated above. I would add the metal needs to be first completely depainted and degreased, acid etched and also a process of Alodine conversion coat applied. Then the Self-etching primer. Then the paint. The best paint job can have disappointing results if corrosion forms between the base metal and the paint job and causes the paint to bubble and fall off. Did I miss anything???